Photographic diffusion transfer process



Jan. 8, 1963 1'. l. ABBOTT ETAL 3,072,480

PHOTOGRAPI-IIC DIFFUSION TRANSFER PROCESS Filed April 10. 1959 st gEXPOSURE DEVELOP/"5N7; TRANSFER OF HAL IDE ION HEAVY METAL SALTRECEPTION SHEET SILVER SAL T AND DEVELOPMENT THOMAS ABBOTT EDWARD C.VAC/(EL @2296 MC M ATTORNEY 8 AGENT States This invention relates to aprocess in photography wherein a product of development ofphotosensitive silver halide, the halide ion, is utilized to produce animage by transfer to a reception layer and conversion to a visible form.v

According to the invention a silver halide emulsion layer is exposed toa subject, then moistened with an alkaline solution in the presence of asilver halide developing agent present either in the alkaline solutionor in the sensitive element itself, and when the emulsion layer isallowed to develop and is placed in contact with an absorbent receptionsurface such as paper, the halide ion produced in development migratesimagewise to the reception surface and is converted to a visible imagethereon.

In one embodiment of the invention the silver halide developing agentused for developing the emulsion layer is initially present in theemulsion layer and development is initiated by application of analkaline solution, the emulsion layer being placed into contact with anabsorbent sheet to transfer the halide ion image thereto, followingwhich the halide image is converted to a visible form, for example, byreaction with a heavy metalsalt followed by reaction with a solublesilver salt and the development of the resulting silver halide image.Alternatively, the transferred halide image may be reacted directly witha soluble silver salt and the resulting silver halide image developed toa silver image.

In a further embodiment of the invention the silver halide emulsion andreception layer are a part of a single photographic element, that is,the layers are coated one over the other. In this case the developingagent may or may not be present in the sensitive element and an alkalinesolution is used to develop the emulsion and cause the transfer of thehalide ion to the reception layer for conversion to a visible image.

One embodiment of our invention is illustrated in Stages 1 to 3 of theaccompanying drawings wherein is shown in greatly enlargedcross-sectional view the appearance of a silver halide emulsion layerduring exposure, development, and transfer of halide ion to a receptionsheet and con version of the resulting heavy metal halide image to avisible silver image. Stage 1 shows the exposure of the sensitiveelement, Stage 2 the emulsion and reception layer in contact during thetransfer of the halide ion image and Stage 3 the final silver printobtained from the halide ion image The following examples will serve toillustrate our invention:

Example 1 A photographic paper comprising a paper support and a gelatinosilver bromoiodide emulsion layer containing the substantiallynondiffusing silver halide developing agent 4-phenyl catechol, wasexposed to a negative subject as shown in Stage 1 of the drawingswherein layer of the element represents the paper support and layer 11the emulsion containing the developing agent, and area 12 the regionofexposure. Development of the emulsion was commenced by bathing it with a4-percent aqueous solution of sodium carbonate for 10 seconds, followedby squeegeeing off the excess solution and pressing the emulsion intocontact with the reception paper 13 (which had been treated with a 15percent solution of lead acetate and atent dried) as shown in Stage 2 ofthe drawings. The halide ion formed in the development of area 12 of theemulsion diffuses imagewise to the reception sheet, reacting with thelead salt to form a lead halide image in area 14. The two elements werethen stripped apart and after briefly washing the sheet with water, itwas treated with a 10 percent solution of silver nitrate which convertedthe lead halide image to silver halide. After washing the sheet for 5minutes it was exposed to light and developed at 68 F. for 2 minutes inthe following developer composition:

. Grams Monomethyl-p-aminophenol sulfate 3 Sodium sulfite, desiccated 45Hydroquinone 12 Sodium carbonate, monohydrate 80 Potassium bromide 2Water to make 1 liter.

As a result of development, a silver image was formed in area 15, asshown in Stage 3 of the drawing. The image had high density and gooddefinition.

Example 2 A photographic emulsion was exposed and treated with carbonatesolution for 10 seconds as described in Example 1. The emulsion was thenpressed into contact with a sheet of common onion skin paper with theresult that the halide released in the development was absorbedimagewise by the paper fibers. The two elements were then stripped apartand the paper carrying the halide image was soaked for 1 minute in 10percent aqueous silver nitrate solution and rinsed in water. The sheetnow carrying a silver halide image was bathed in an oxidizing bath of 2grams of potassium dichromate and 2 cc. of concentrated sulfuric acidper liter of water in order to remove silver present in the non-imageareas thus leaving only a silver halide image on the sheet. Afterwashing the sheet it was exposed to light and developed as described inExample 1 to obtain a positive silver image from the original negative.The silver image had high density and sharpness.

In a procedure similar to that of Example 1, after transfer of thehalide image to the reception sheet containing heavy metal salt such aslead acetate, the resulting heavy metal halide image may be treated withsodium sulfide solution to convert the metal halide image to a coloredmetal sulfide image.

In the processes described, the silver halide developing agent used inthe initial development step may be contained in the alkaline solutionused for development rather than in the emulsion layer itself. The moresoluble developing agents such as hydroquinone, monomethyl-paminophenolsulfate, 3-pyrazolidones, etc., are suitable for this purpose.

The silver halide of the emulsion layer is not especially critical,useful results being obtained with, for example, silver bromide, silverbromoiodide or silver chloride emuls1ons.

In the initial development step it is advantageous to use a minimumamount of agitation to insure that the halide ion does not difiusethrough the emulsion layer to any great extent.

In a manner similar to the above examples, the processes can be carriedout with a multilayer element having a support carrying a precipitantfor halide ion such as lead salt and thereover a removable silver halideemulsion layer such as a cellulose ether phthalate silver halideemulsion layer. On development of the emulsion layer, halide ionmigrates imagewise from the developed regions to the underlying layerwhere it reacts with the precipitant for the halide ion. At this stagethe emulsion layer may be rubbed off or otherwise removed and the metalhalide image remaining on the support may be treated as described aboveto increase its optical density.

The photographic emulsions used in practicing our invention are of thedeveloping-out type.

The emulsions can be chemically sensitized by any of the acceptedprocedures. The emulsions can be digested with naturally active gelatin,or sulfur compounds can be added such as those described in SheppardU.S. Patent 1,574,944, issued March 2, 1926, Sheppard et al. U.S. Patent1,623,499, issued April 5, 1927, and Sheppard et a1. U.S. Patent2,410,689, issued November 5, 1946.

The emulsions can also be treated with salts of the noble metals such asruthenium, rhodium, palladium, iridium, and platinum. Representativecompounds are ammonium chloropalladate, potassium chloroplatinate, andsodium chloropalladite, which are used for sensitizing in amounts belowthat which produces any substantial fog inhibition, as described inSmith and Trivelli U.S. Patent 2,448,060, issued August 31, 1948, and asanti-foggants in higher amounts,- as described in Trivelli and SmithU.S. Patents 2,566,245, issued August 28, 1951, and 2,566,263, issuedAugust 28, 1951.

The emulsions can also be chemically sensitized With gold salts asdescribed in Waller et a1. U.S. Patent 2,399,- 083, issued April 23,1946, or stabilized with gold salts as described in Damschroder U.S.Patent 2,597,856, issued May 27, 1952, and Yutzy and Leermakers U.S.Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassiumchloroaurite, potassium aurithiocyanate, potassium chloroaurate, aurictrichloride and 2- aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agentssuch as stannous salts (Carroll U.S. Patent 2,487,850, issued November15, 1949), polyamines, such as diethyl triamine (Lowe and Jones U.S.Patent 2,518,- 698, issued August 15, 1950), polyamines, such asspermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12,1950), or bisUB-aminoethyl) sulfide and its water-soluble salts (Loweand Jones U.S. Patent 2,521,- 926, issued September 12, 1950).

The emulsions can also be optically sensitized with cyanine andmerocyanine dyes, such as those described in Brooker U.S. Patents1,846,301, issued February 23, 1932; 1,846,302, issued February 23,1932; and 1,942,854, issued January 9, 1934; White U.S. Patent1,990,507, issued February 12, 1935; Brooker and White U.S. Patents2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939;2,493,747, issued January 10, 1950; and 2,739,- 964, issued March 27,1956; Brooker and Keyes U.S. Patent 2,493,748, issued January 10, 1950;Sprague U.S. Patents 2,503,776, issued April 11, 1950; and 2,519,001,issued August 15, 1950; Heseltine and Brooker U.S. Patent 2,666,761,issued January 19, 1954; Heseltine U.S. Patent 2,734,900, issuedFebruary 14, 1956; Van Lare U.S. Patent 2,739,149, issued March 20,1956; and Kodak Limited British Patent 450,958, accepted July 15, 1936.

The emulsions can also be stabilized with the mercury compounds ofAllen, Byers and Murray U.S. Patent 2,- 728,663, issued December 27,1955; Carroll and Murray U.S. Patent 2,728,664, issued December 27,1955; and Leubner and Murray U.S. Patent 2,728,665, issued December 27,1955; the triazoles of Heimbach and Kelly U.S. Patent 2,444,608, issuedJuly 6, 1948; the azaindenes of Heirnbach and Kelley U.S. Patents2,444,605 and 2,444,606, issued July 6, 1948; Heimbach U.S. Patents2,444,607, issued July 6, 1948, and 2,450,397, issued September 28,1948; Heimbach and Clark U.S. Patent 2,444,609, issued July 6, 1948;Allen and Reynolds U.S. Patents 2,713,541, issued July 19, 1955, and2,743,181, issued April 24, 1956; Carroll and Beach U.S. Patent 2,-716,062, issued August 23, 1955; Allen and Beilfuss U.S. Patent2,735,769, issued February 21, 1956; Reynolds and Sagal U.S. Patent2,756,147, issued July 24, 1956; Allen and Sagura U.S. Patent 2,772,164,issued November 27,

1956, and those disclosed by Birr in Z. wiss. Phot. vol. 47, 1952, pages2-28; the disulfides of Kodak Belgian Patent 569,317, issued July 31,1958; the quaternary benzothiazolium compounds of Brooker and Staud U.S.Patent 2,131,038, issued September 27, 1938, or the polymethylenebis-benzothiazolium salts of Allen and Wilson U.S. Patent 2,694,716,issued November 16, 1954; or the zinc and cadmium salts of Jones U.S.Patent 2,839,405, issued June 17, 1958.

The emulsions may also contain speed-increasing compounds of thequaternary ammonium type of Carroll U.S. Patent 2,271,623, issuedFebruary 3, 1942; Carroll and Allen US. Patent 2,288,226, issued June30, 1942; and Carroll and Spence U.S. Patent 2,334,864, issued Novemoer23, 1943; and the polyethylene glycol type of Carroll and Beach U.S.Patent 2,708,162, issued May 10, 1955.

The emulsions may contain a suitable gelatin plasticizer such asglycerin; a dihydroxy alkane such as 1,5- pentane diol as described inMilton and Murray U.S. application Serial No. 588,951, filed June 4,1956; an ester of an ethylene bis-glycolic acid such as ethylene bis(methyl glycolate) as described in Milton U.S. application Serial No.662,564, filed May 31, 1957; bis-(ethoxy diethylene glycol) succinate asdescribed in Gray U.S. application Serial No. 604,333, filed August 16,1956, or a polymeric hydrosol as results from the emulsionpolymerization of a mixture of an amide of an acid of the acrylic acidseries, an acrylic acid ester and a styrenetype compound as described inTong U.S. Patent 2,852,- 386, issued September 16, 1958. The plasticizermay be added to the emulsion before or after the addition of asensitizing dye, if used.

The emulsions may be hardened with any suitable hardener for gelatinsuch as formaldehyde; a halogen-substituted aliphatic acid such asmucobromic acid as described in White U.S. Patent 2,080,019, issued May11, 1937; a compound having a plurality of acid anhydride groups such as7,8-diphenylbicyclo (2,2,2)-7-octene-2,3,5,6-tetracarboxylicdianhydride, or a dicarboxylic or a disulfonic acid chloride such asterephthaloyl chloride or naphthalene-1,5-disulfonyl chloride asdescribed in Allen and Carroll U.S. Patents 2,725,294, and 2,725,295,both issued November 29, 1955; a cyclic 1,2-diketone such ascyclopentane-1,2-dione as described in Allen and Byers U.S. Patent2,725,305, issued November 29, 1955; a bisester of methane-sulfonic acidsuch as 1,2-di-(methane-sulfonoxy)-ethane as described in Allen andLaakso U.S. Patent 2,726,162, issued December 6, 1955;1,3-dihydroxymethylbenzimidazol-2-one as described in July, (nott andPollak U.S. Patent 2,732,316, issued January 24, 1956; a dialdehyde or asodium bisulfite derivative thereof, the aldehyde groups of which areseparated by 23 carbon atoms, such as B-methyl glutaraldehyde bis-sodiumbisulfite as described in Allen and Burness U.S. Patent applicationSerial No. 556,031, filed December 29, 1955; a bis-aziridine carboxamidesuch as trimethylene bis(laziridine carboxamide) as described in Allenand Webster U.S. patent application Serial No. 599,891, filed July 25,1956; or 2,3-dihydroxy dioxane as described in Jeffreys U.S. Patent2,870,013, issued January 20, 1959.

The emulsions may contain a coating aid such as saponin; a lauryl oroleyl monoether of polyethylene glycol as described in Knox and DavisU.S. Patent 2,831,766, issued April 22, 1958; a salt of a sulfated andalkylated polyethylene glycol ether as described in Knox and Davis U.S.Patent 2,719,087, issued September 27, 1955; an acylated alkyl taurinesuch as the sodium salt of N-oleoyl-N-methyl taurine as described inKnox, Twardokus and Davis U.S. Patent 2,739,891, issued March 27, 1956;the reaction product of a dianhydride of tetracarboxybutane with analcohol or an aliphatic amine containing from 8 to 18 carbon atoms whichis treated With a base, for example, the sodium salt of the monoester oftetracarboxybutane as described in Knox,

Stenberg and Wilson U.S. Patent 2,843,487, issued July 15, 1958; awater-soluble maleopimarate or a mix ture of a water-solublemaleopimarate and a substituted glutamate salt as described in Knox andFowler U.S. Patent 2,823,123, issued February 11, 1958; an alkali metalsalt of a substituted amino acid such as disodium N-carbo-p-tert.octylphenoxypentaethoxy)glutamate as described in Knox and Wilson U.S.patent application Serial No. 600,679, filed July 30, 1956; or asulfosuccinamate such as tetrasodium N-(1,2-dicarboxyethyl)-N- octadecylsulfosuccinamate or N-lauryl disodium sulfosuccinamate as described inKnox and Stenberg U.S. patent application Serial No. 691,125, filedOctober 21, 1957.

In the preparation of the silver halide dispersions employed forpreparing silver halide emulsions, there may be employed as thedispersing agent for the silver halide in its preparation, gelatin orsome other colloidal material .such as colloidal albumin, a cellulosederivative, or a synthetic resin, for instance, a polyvinyl compound.Some colloids which may be used are polyvinyl alcohol or a hy drolyzedpolyvinyl acetate as described in Lowe U.S. Patent 2,286,215, issuedJune 16, 1942; a far hydrolyzed cellulose ester such as celluloseacetate hydrolyzed to anacetyl content of 19-26% as described in U.S.Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; awater-soluble ethanolamine cellulose acetate as described in Yutzy U.S.Patent 2,322,085, issued June 15, v1943; a polyacrylamine having acombined acrylamide content of 30-60% and a specific viscosity of 025+1.5 on an imidized polyacrylamide of like acrylamide content andviscosity as described in Lowe, Minsk and Kenyon U.S. Patent 2,541,474,issued February 13, 19,51; zein as described in Lowe U.S. Patent2,563,791, issued August 7, 1951; a vinyl alcohol polymer containingurethane carboxylic acid groups of the type described in Unruh and SmithU.S. Patent 2,768,l54,-issued October 23, 1956; or containingcyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetatecopolymer as described in Unruh, Smith and PriestUS. Patent 2,808,331,is sued October 1, 1957; or a polymeric material which results frompolymerizing a protein or a saturated acylated protein with a monomerhaving a vinyl group as described in U.S. Patent 2,852,382, ofIllingsworth, Dann and Gates, issued September 16, 1958.

If desired, compatible mixtures of two or more of these colloids may beemployed for dispersing the silver halide in its preparation.Combinations of these antifoggants, sensitizers, hardners, etc., may beused.

What we claim is:

l. A photographic diffusion transfer process for produring negativeimages comprising I (a) exposing a developing-out type silver halideemulsion layer to a subject,

([2) imbibing in said exposed emulsion layer an aqueous alkalinesolution while the silver halide of said emulsion layer is in contactwith a silver halide developing agent, but in the substantial absence ofsilver halide solvent, thereby forming in said silver halide emulsionlayer a visible image comprising negative silver and halide ion,

(c) diffusing said halide ion'from the negative image areas only of saidemulsion layer to a contiguous, light-insensitive, absorbent layercontaining a lead salt soluble in aqueous alkaline solutions leavingunexposed, undeveloped silver halide in said emulsion layer, therebyforming a lead halide latent image from said diffused halide ion, and

(d) converting the resultant lead halide latent image to a visibleimage.

2. A photographic diffusion transfer process for producing negativeimages comprising (a) exposin a dev oning-out type silver halideemulsion layer to a subject, (b) imbibing in said exposed emulsion layeran aqueous alkaline solution while the silver halide of said emulsionlayer is in contact with a silver halide developing agent, but in thesubstantial absence of silver halide solvent, thereby forming in saidsilver halide emulsion layer a visible image comprising negative silverand halide ion,

(0) diffusing said halide ion from the negative image areas only of saidemulsion layer to a contiguous, light-insensitive, absorbent layercontaining a lead salt soluble in aqueous alkaline solutions leavingunexposed, undeveloped silver halide insaid emulsion layer, therebyforming a lead halide latent image from said diffused halide ion, and

(d) converting the resultant lead halide latent image to a visible imagewith a soluble silver salt.

3. A photographic diifusion transfer process for producing negativeimages comprising (a) exposing a developing-out type silver halideemulsion layer to a subject,

(b) imbibing in said exposed emulsion layer an aqueous alkaline solutionwhile the silver halide of said emulsion layer is in contact with asilver halide developing agent, but in the substantial absence of silverhalide solvent, thereby forming in said silver halide emulsion layer avisible image comprising negative silver and halide ion,

(c) diffusing said halide ion from the negative image areas only of saidemulsion layer to a contiguous, light-insensitive, absorbent layercontaining a lead salt soluble in aqueous alkaline solutions leavingunexposed, undeveloped silver halide in said emulsion layer, therebyforming a lead halide latent image from said diffused halide ion, and

(d) converting the resultant lead halide latent image to a visible imagewith a sulfide solution.

4. A photographic diffusion transfer process for producing negativeimages comprising (a) exposing a developing-out type silver halideemulsion layer to a subject,

(b) imbibing in said exposed emulsion layer an aqueous alkaline solutionwhile the silver halide of said emulsion layer is in contact with asilver halide developing agent, but in the substantial absence of silverhalide solvent, thereby forming in said silver halide emulsion layer avisible image comprising negative silver and halide ion,

(c) diffusing said halide ion from the negative image areas only of saidemulsion layer to a contiguous, light-insensitive, absorbent layerleaving unexposed, undeveloped silver halide in said emulsion layer, and

(d) converting the resultant halide ion latent image to a visible imagewith soluble silver salt.

' 5. A photographic diffusion transfer process for producing negativeimages comprising ('a) exposing a developing-out type silver halideemulsion layer to a subject,

(b) imbibing in said exposed emulsion layer an aqueous alkaline solutionwhile the silver halide of said emulsion layer is in contact with asilver halide developing agent, but in the substantial absence of silverhalide solvent, thereby forming in said silver halide emulsion layer avisible image comprising negative silver and halide ion,

(0) diffusing said halide ion from the negative image areas only of saidemulsion layer to a contiguous, light-insensitive, absorbent layercontaining a lead salt soluble in aqueous alkaline solutions leavingunexposed, undeveloped silver halide in said emulsion layer, the leadhalide being less soluble than said lead salt which is soluble inaqueous alkaline solutions, thereby forming a lead halide latent imagefrom said difiused halide ion, and

(d) converting the resultant lead halide latent image to a visibleimage.

3,072,480 7 8 6. A photographic diffusion transfer process forprodiffusing said halide ion from the negative image ducing negativeimages comprising areas only of said emulsion layer to a contiguous,

(a) exposing a developing-out type silver halide emullight-insensitive,absorbent layer containing lead acesion layer to a subject, tate leavingunexposed, undeveloped silver halide in (b) imbibing in said'exposedemulsion layer an aqueous said emulsion layer, thereby forming a leadhalide alkaline solution While the silver halide of said emullatentimage from said diffused halide ion, and

sion layer is in contact with a silver halide developing (d) convertingthe resultant lead halide latent image agent, but in the substantialabsence of silver halide to a visible image.

solvent, thereby forming in said silver halide emul- 9. A photographicdiffusion transfer process for prosion layer a visible image comprisingnegative silver 10 ducing negative images comprising and halide ion, (a)exposing a developing-out type silver halide emul- (c) diffusing saidhalide ion from the negative image sion layer to a subject,

areas only of said emulsion layer to a contiguous, (b) imbibing in saidexposed emulsion layer an aqueous light-insensitive, absorbent layercontaining a lead salt soluble in aqueous alkaline solutions leavingunexposed, undeveloped silver halide in said emulsion layer, the leadhalide being less soluble than said lead salt Which is soluble inaqueous alkaline solutions, thereby forming a lead halide latent imagefrom said (c) diffusing said halide ion from the negative image areasonly of said emulsion layer to a contiguous, light-insensitive,absorbent layer containing lead acetate leaving unexposed, undevelopedsilver halide in said emulsion layer, thereby forming a lead halidelatent image from said diffused halide ion, and

(d) converting the resultant lead halide latent image to a visible imagewith a soluble silver salt.

10. A photographic diffusion transfer process for producing negativeimages comprising (a) exposing a developing-out type silver halideemulsion layer to a subject,

(b) imbibing in said exposed emulsion layer an aqueous alkaline solutionWhile the silver halide of said emulsion layer is in contact with asilver halide developing agent, but in the substantial absence of silverhalide difiused halide ion, and

(d) converting the resultant lead halide latent image to a visible imagewith a sulfide solution.

7. A photographic diffusion transfer process for producing negativeimages comprising (a) exposing a developing-out type silver halideemulsion layer to a subject,

(b) imbibing in said exposed emulsion layer an aqueous alkaline solutionwhile the silver halide of said emulsion layer is in contact with asilver halide developing agent, but in the substantial absence of silver0 halide solvent, thereby forming in said silver halide emulsion layer avisible image comprising negative silver and halide ion,

(c) diffusing said halide ion from the negative image areas only of saidemulsion layer to a contiguous,

(d) converting the resultant lead halide latent image to a visible imageWith a soluble silver salt.

solvent, thereby forming in said silver halide emulsion layer a visibleimage comprising negative silver and halide ion,

(c) dilfusing said halide ion from the negative image areas only of saidemulsion layer to a contiguous, light-insensitive, absorbent layercontaining lead acetate leaving unexposed, undeveloped silver halide insaid emulsion layer, thereby forming a lead halide latent image fromsaid diffused halide ion, and

(d) converting the resultant lead halide latent image 8. A photographicdiffusion transfer process for proto a visible image With sulfidesolution.

ducing negative images comprising (a) exposing a developing-out typesilver halide emulsion layer to a subject, (b) imbibing in said exposedemulsion layer an aqueous alkaline solution While the silver halide ofsaid emul- References Cited in the file of this patent UNITED STATESPATENTS sion layer is in contact with a silver halide develop- 2698238Land 1954 2,705,676 Land et al. Apr. 5, 1955 mg agent, but in thesubstantial absence of silver 2,712,995 Weyde July 12, 1955 halidesolvent, thereby forming 1n said silver halide W M emulsion layer avisible ima comprisin" negative 2937945 eyde et ay 1960 Silver andhalide 2,952,537 Blake et al Sept. 13, 1960

4. A PHOTOGRAPHIC DIFFUSION TRANSFER PROCESS FOR PRODUCING NEGATIVEIMAGES COMPRISING (A) EXPOSING A DEVELOPING-OUT TYPE SILVER HALIDEEMULSION LAYER TO A SUBJECT, (B) IMBIBING IN SAID EXPOSED EMULSION LAYERAN AQUEOUS ALKALINE SOLUTION WHILE THE SILVER HALIDE OF SAID EMULSIONLAYER IS IN CONTACT WITH A SILVER HALIDE DEVELOPING AGENT, BUT IN THESUBSTANTIAL ABSENCE OF SILVER HALIDE SOLVENT, THEREBY FORMING IN SAIDSILVER HALIDE EMULSION LAYER A VISIBLE IMAGE COMPRISING NEGATIVE SILVERAND HALIDE ION, (C) DIFFUSING SAID HALIDE ION FROM THE NEGATIVE IMAGEAREAS ONLY OF SAID EMULSION LAYER TO A CONTIGUOUS, LIGHT-INSENSITIVE,ABSORBENT LAYER LEAVING UNEXPOSED, UNDEVELOPED SILVER HALIDE IN SAIDEMULSION LAYER, AND (D) CONVENTING THE RESULTANT HALIDE ION LATENT IMAGETO A VISIBLE IMAGE WITH SOLUBLE SILVER SALT.